This application claims priority benefits of a prior filed Japanese application number 2001-137217, filed May 8, 2001.
The present invention relates to a compact and multiple optical fiber coupler and, more particularly, to a compact and multiple optical fiber coupler of the type that plural optical fiber couplers having their stripped portions fused to each other and drawn or tapered together are integrally joined to a common substrate and enclosed in the same package or capsule. The invention also pertains to a method of making the compact and multiple optical fiber coupler.
A description will be given first, with reference to FIG. 1, of a prior art example which is a 2-by-2 fusion taper type optical fiber coupler indicated generally by 10. In FIG. 1, stripped portions 12a and 12b of two optical fibers 11a and 11b are first aligned in parallel contacting relation and then fused together and drawn or tapered to form a coupler portion 13, which is fixed onto the surface of a substrate 15, and the whole of the fused-tapered coupler portion 13 including the substrate 15 is enclosed in the same package or capsule 16. The stripped portions 12a and 12b are fused and drawn or tapered to form the fused-tapered coupler portion 13 by such a method as shown in FIG. 2A. That is, the stripped portions 12a and 12b of the pair of optical fibers 11a and 11b clamped in parallel relation are firmly gripped between two pairs of spaced-apart pins P1a, P1b and P2a, P2b so that they are aligned in parallel contacting relation, and the intermediate parallel contacting portions of the stripped optical fibers are fused together by heating with the flame 21 of a gas burner and tapered to form the coupler portion 13. Alternatively, the optical fibers 11a and 11b are arranged with their stripped portions 12a and 12b held in crossing relation and fusion-tapered into a coupler portion as shown in FIG. 2B.
FIG. 3 shows an example of a two-in-one package optical fiber coupler in which two 2-by-2 fusion taper type optical fiber couplers 10-1 and 10-2, produced separately by the method described above with reference to FIG. 1, are enclosed in a common package or capsule 160.
FIG. 4 schematically depicts another prior art example of a multiple optical fiber coupler, which is a 2-by-4 tree optical fiber coupler in which three 2-by-2 optical fiber couplers 10-1, 10-2 and 10-3 similar to that mentioned above in respect of FIG. 1 are enclosed in the package 160. The illustrated 2-by-4 tree optical fiber coupler is a multiple optical fiber coupler in which the fused-tapered coupler portions 13-1 and 13-2 of the two 2-by-2 optical fiber couplers 10-1 and 10-2 are arranged in parallel relation and inner adjacent stripped portions 12b-1 and 12a-2 are connected to stripped portions 12a-3 and 12b-3 of the 2-by-2 optical fiber coupler 10-3, respectively. This multiple optical fiber coupler is also enclosed in the common package or capsule 160.
Since the conventional multiple optical fiber coupler of FIG. 3 has a construction that the two 2-by-2 fusion taper type optical fiber couplers 10-1 and 10-2 enclosed in the packages 16-1 and 16-2, respectively, are housed in the one package 160, the outer dimension of the package 160 is larger than the outer dimension of the 2-by-2 optical fiber coupler 10 of FIG. 1, approximately twice in diameter. For example, the package 16 in FIG. 1 is about 3 mm in diameter and about 50 mm in length, whereas the package 160 in FIG. 3 is around 6 mm in diameter and around 50 mm in length.
Also in the case of the conventional multiple optical fiber coupler of FIG. 4 in which three 2-by-2 optical fiber couplers 10 each enclosed in the package 16 depicted in FIG. 1 are connected as described above, the package 160 is approximately twice larger than the individual package 16 in length as well as in diameter.
It is therefore an object of the present invention to provide a compact and multiple optical fiber coupler of the type that plural optical fiber couplers having their stripped portions fused together and tapered are integrally joined to the same substrate and enclosed in the same package so as to solve the above-mentioned problems of the prior art, and a method of making the compact and multiple optical fiber coupler.
The multiple optical fiber coupler according to the present invention comprises:
at least three optical fibers arranged adjacent one another;
at least two coupler portions formed by fusing and tapering at least two of said at least three optical fibers;
a substrate having fixedly arranged on one side thereof said at least two coupler portions; and
a package for enclosing said at least two coupler portions and said substrate;
wherein said at least two optical fibers are extended out of said package from said at least two coupler portions enclosed in said package.
The method of making a multiple optical fiber coupler having at least two coupler portions according to the present invention comprises the steps of:
(a) arranging in parallel relation more than two optical fibers each having a stripped portion so that said stripped portions of a first pair of those adjacent ones of said more than two optical fibers contact with each other to form a first mating alignment portion and that said stripped portions of a second pair of those adjacent ones of said more than two optical fibers whose one optical fiber differs from one of the optical fibers of said first pair contact with each other to form a second mating alignment portion at a distance from said first mating alignment portion in the direction of extension of said more than two optical fibers, and clamping said more than two optical fibers at opposite sides of said stripped portions;
(b) simultaneously heating and drawing all of said more than two optical fibers in a first area containing said first mating alignment portion to fuse said first mating alignment portion to form a first coupler portion;
(c) simultaneously heating and drawing all of said more than two optical fibers in a second area containing said second mating alignment portion to fuse said second mating alignment portion to form a second coupler portion;
(d) fixing said stripped portions of all of said more than two optical fibers, including said first and second coupler portions, to one side of a common substrate; and
(e) hermetically sealing said stripped portions, including said first and second coupler portions, and whole of said substrate in a package.